In general, among the granulating and coating techniques for powdery material, such a type of technique is known that respective spray nozzles for supplying powdery material as articles to be coated and for supplying a coating liquid as coating material are disposed to be opposed to each other in a diametral direction of a vertical coating cylinder and dry air stream such as hot air is supplied from thereunder.
Furthermore, there is also known another type where two spray nozzles are provided in erected postures and generally in parallel to each other.
However, according to the spray nozzle technique of the above-described opposedly disposed type, it is difficult to maintain equal blow-out force between these spray nozzles, when the articles to be coated and the coating material should collide with each other from opposite directions.
When, for example, the blow-out force of the coating liquid is stronger, such disadvantages occurs that the coating material adheres to an opposed inner wall surface of the coating apparatus to be solidified thereon, or, before solidifying of the coating material, the articles to be coated adhere onto the coating material on the wall to be agglomerated there.
Furthermore, due to the unbalance in the blow-out forces or in the blown-out rate, there may be disadvantage that the coating liquid becomes particles by itself through the so-called spray dry phenomenon without adhering to and forming coat on the articles to be coated.
Furthermore, according to the above-described technique of parallelly disposed spray nozzles, the powdery material and the coating liquid are supplied from the substantially same direction, so that the efficiency of contact therebetween may be in low level.
It is an object of the present invention to provide a technique wherein the probabilities of contact between the powdery material and the coating liquid is raised so that coating is performed efficiently.
It is another object of the present invention to provide a technique wherein reliable coating can be performed by use of one spray nozzle.